O字開頭的單詞或詞組
outflowovershadowon saleottoon holidayon the telephoneoperationalorienteeringophthalmologyoverallsoxideonlookeroppressionovereatoxidativeolfactoryobserveron the increaseoutnumberoverstressomnivoreoo-on tapoverstateoutwardlyocelotover-orificeout of dangeroutward-boundob-onerousorthopedicsorthogonalon leaveolefinoutside loopoximeteroutput powerOregonophthalm-oatmeal